1. Field of the Invention
The present invention relates to a semiconductor device, in particular, to a semiconductor device for power which withstands a high voltage.
2. Description of the Background Art
FIG. 29 shows a cross section view of the structure of the semiconductor device M70 as an example of a conventional semiconductor device. As shown in FIG. 29, in the semiconductor device M70, for example, an insulating substrate 102 is mounted on a base plate 104 formed of oxygen-free copper and a semiconductor element 101, which is a switching element, is mounted on this insulating substrate 102. On the insulating substrate 102, a predetermined conductor pattern is provided on one of the main surfaces of the insulating substrate and a semiconductor element, or the like, is provided on this conductor pattern. In addition, a conductor layer is provided on the other main surface so as to provide a structure that can be adhered to a conductor plate, or the like, by means of soldering, or the like.
A resin case 105 which is formed of, for example, PPS (polyphenylene sulphide) is provided so as to surround the peripheral parts of the base plate 104.
The resin case 105 is provided with an electrode plate DE which is formed of an external connection electrode plate 108, a connection conductor 106 and an internal connection electrode 107 so as to be partially buried. The internal connection electrode 107 is electrically connected to the semiconductor element 101 or to the conductor pattern of the insulating substrate 102 through an aluminum wire 109 of the diameter of 200 xcexcm to 300 xcexcm.
Then, the internal space defined by the base plate 104 and the resin case 105 is filled in with, for example, silicone gel 110 in order to secure the insulation and a lid 111 is provided over the opening of the resin case 105 in order to block the silicone gel 110 from the air outside.
In addition, part of the main surface of the external connection electrode plate 108 is exposed on the main surface of the resin case 105 and a through hole is created in such part for the connection with an external conductor (not shown) while a nut 112 is buried in the resin case 105 in the place which corresponds to this through hole. Accordingly, the external connection electrode plate 108 and the external conductor can be connected by using a bolt (not shown) so that the contact resistance can be made small by fastening the bolt.
In this manner, a configuration wherein the semiconductor element 101 is contained in the resin case 105 is adopted in the semiconductor device M70 and, therefore, the manufacturing process becomes complicated, the dimensions of the external form become large and miniaturization or cost reduction are limited.
In addition, FIG. 30 shows a cross section view of the configuration of the semiconductor device M80 as an example of a conventional semiconductor device.
As shown in FIG. 30, in the semiconductor device M80, a semiconductor element 201 which is a switching element is mounted on a frame 213 which is formed of, for example, a copper alloy and the semiconductor element 201 is electrically connected to the lead 207 through an aluminum wire 209.
The semiconductor element 201, the lead 207 and the frame 213 are sealed in a mold resin 214 by using a transfer molding so as to be integrated. Then, a part of the lead 207 and a part of a lead 215 which extends from the frame 213 protrude to the outside from the mold resin 214 so as to be soldered to, for example, a printed circuit board which has through holes.
In this manner, though in the semiconductor device M80, the semiconductor element 201 is sealed in a resin by using transfer molding so that the number of parts is small and the cost can be held low, the heat emitted by the semiconductor element 201 at the time of the operation is radiated through the mold resin 214 of which the heat conductance is several Wmxc2x7K with a high heat resistance so as to have a problem radiating heat.
In addition, the lead 207 is thin and the cross section area of the lead 207 and the cross section area of the circuit pattern on the printed circuit board for allowing a heavy current to flow to which the lead 207 is connected cannot be sufficiently secured and, therefore, the loss due to the electrical resistance cannot be ignored and there is the problem that the lead is not suitable for a semiconductor device for a heavy current.
In addition, FIG. 31 shows a cross section view of the configuration of the semiconductor device M90 as an example of a conventional semiconductor device.
As shown in FIG. 31, in the semiconductor device M90, a semiconductor element 301 which is a switching element is mounted on an insulating substrate 302 and the semiconductor element 301 is electrically connected to a lead 315 through an aluminum wire 309. Then, the insulating substrate 302, the semiconductor element 301 and the lead 315 are sealed in a mold resin 314 by using transfer molding so as to be integrated.
A main surface of the insulating substrate 302 opposite to the main surface, on which the semiconductor element 301 is mounted, is exposed from the mold resin 314 and is soldered to a metal substrate 304. In addition, a control circuit substrate 317 or a relay substrate 318 are also provided on the metal substrate 304.
The control circuit substrate 317 is a substrate on which a control circuit, or the like, for controlling the operation of the semiconductor element 301 is provided and the relay substrate 318 is a substrate to which a relay point of the lead 315 is provided.
The leads 315 which extend from mold resin 314 are connected to the relay substrate 318 and a conductor layer 319 which is provided on the control circuit substrate 317 and the lead 315 which is connected to the relay substrate 318 is electrically connected to the external connection electrode plate 316 via the conductive layer 319 and the lead 315 connected to the control circuit substrate 317 is connected to a control terminal 320 via the conductive layer 319.
In this manner, in the semiconductor device M90, the insulating substrate 302, on which the semiconductor element 301 is mounted, contacts the metal substrate 304 and, therefore, the semiconductor device M90 is superior to the semiconductor device M80 concerning the radiation of heat. However, the control circuit substrate 317 and the relay substrate 318 are separately provided on the metal substrate 304 and, therefore, layout efficiency is poor and there is the problem that miniaturization is difficult.
In addition, the area of the loop circuit, which is formed starting from and reaching to the external connection electrode plate 316 via the relay substrate 318, the lead 315, one of the main electrodes of the semiconductor element 301, the other main electrode, the relay substrate 318 and the lead 315, becomes large so as to have a large inductance and this becomes a factor leading to the occurrence of a large surge voltage. Therefore, the change ratio of the current becomes large in the case that the semiconductor element 301 is operated in a switching manner and, therefore, an element which withstands a high voltage must be prepared and this becomes a factor leading to an increase in the cost.
As described above, in a conventional semiconductor device, it is difficult to satisfy both the requirements concerning the radiation of heat and concerning miniaturization.
According to the first aspect of the present invention, a semiconductor device comprises a radiation substrate, semiconductor elements provided on the radiation substrate, a plurality of main electrode plates of which one end is electrically connected to a main electrode of the semiconductor elements, respectively and a resin package for sealing the radiation substrate, the semiconductor elements and the plurality of main electrode plates in a resin, wherein the other end of each of the plurality of main electrode plates is exposed to the outside of the upper surface of the resin package and wherein the resin package is integrally formed by means of molding.
According to the second aspect of the present invention, in the semiconductor device, the resin package is in a box shape and a main surface of the other end of each of the plurality of main electrode plates alone is exposed on the upper surface of the resin package.
According to the third aspect of the present invention, in the semiconductor device, the exposure position of the main surface of the other end of each of the plurality of main electrode plates is a position near a center of the upper surface of the resign package.
According to the fourth aspect of the present invention, in the semiconductor device, the resin package has a body part in a box shape and a plurality of protruding electrode parts which, respectively, protrude from the upper surface of the body part and contain the plurality of main electrode plates within the inside and the main surface of the other end of each of the plurality of main electrode plates alone is exposed on the upper surface of each of the plurality of protruding electrode parts.
According to the fifth aspect of the present invention, in the semiconductor device, the plurality of protruding electrode parts are formed so that the bordering parts between the plurality of protruding electrode parts and the body part have curved surfaces.
According to the sixth aspect of the present invention, in the semiconductor device, the plurality of protruding electrode parts are provided at peripheral parts of the body part and have cavities inside thereof; and the other end of each of the plurality of main electrode plates is provided so as to cover the upper of each of the cavities.
According to the seventh aspect of the present invention, in the semiconductor device, the other end of each of the plurality of main electrode plates has a through hole and the through hole has a thread around the inner surface thereof.
According to the eighth aspect of the present invention, in the semiconductor device, the through hole is created by means of a burring process and the thread is provided on a burring part which protrudes to the side of the cavity by means of the burring process.
According to the ninth aspect of the present invention, in the semiconductor device, the other end of each of the plurality of main electrode plates has a through hole and the plurality of protruding electrode parts further have nuts buried therein so that the thread of each of the nuts are connected to that of the through hole.
According to the tenth aspect of the present invention, in the semiconductor device, the semiconductor device further comprises a control circuit which is provided on the radiation substrate and which carries out a driving control of the semiconductor elements.
According to the eleventh aspect of the present invention, in the semiconductor device, the control circuit is covered with a resin of which the viscosity is smaller than that of the mold resin of the resin package.
According to the twelfth aspect of the present invention, in the semiconductor device, a bottom surface of the radiation substrate, that is the opposite side of the surface on which the semiconductor elements are mounted, is exposed from the bottom surface of the resin package and the semiconductor device further comprises an insulating layer provided on the side of the bottom surface of the resin package so as to, at least, completely cover the bottom surface of the radiation substrate.
According to the thirteenth aspect of the present invention, in the semiconductor device, the insulating layer is formed of an insulating material in a sheet form attached to the bottom surface of the resin package.
According to the fourteenth aspect of the present invention, in the semiconductor device, the bottom surface of the resin package has a step region which is recessed and corresponds to the exposure region of the bottom surface of the radiation substrate and the depth of the step region is lower than the thickness of the insulating layer.
According to the fifteenth aspect of the present invention, in the semiconductor device, the bottom surface of the resin package has a plurality of protruding parts which are provided so as to surround the exposure region of the bottom surface of the radiation substrate and the height of the protruding parts is lower than the thickness of the insulating layer.
According to the sixteenth aspect of the present invention, the semiconductor device further comprises a radiation plate which closely contacts on the insulating layer and of which the area is broader than that of the insulating layer.
According to the seventeenth aspect of the present invention, a semiconductor device comprises a plurality of radiation substrates, semiconductor elements respectively provided on the plurality of radiation substrates, a plurality of main electrode plates of which one end is electrically connected to a main electrode of each of the semiconductor elements, respectively, and a resin package for sealing the plurality of radiation substrates, the semiconductor elements and the plurality of main electrode plates in a resin, wherein the other end of each of the plurality of main electrode plates is exposed to the outside of the upper surface of the resin package and wherein the resin package is integrally formed by means of molding.
According to the eighteenth aspect of the invention, in the semiconductor device, all of the plurality of radiation substrates have a same rectangular shape and are arranged so that the long sides thereof are parallel to each other.
In accordance with a semiconductor device according to the first aspect of the present invention, the other end of each of the plurality of main electrode plates is exposed to the outside of the upper surface of the resin package and the resin package is integrally formed by means of molding and, therefore, the components can be effectively arranged and the dimension of the external form of the radiation substrate can be made approximately as large as the dimension of the external form of the resin package so that the miniaturization becomes possible while maintaining the radiation performance. In addition, since the plurality of the main electrode plates are provided so as to be exposed on the upper surface of resin package and, therefore, the area of the loop circuit formed of the plurality of the main electrode plates and an electric path that electrically connects these electrodes becomes small so that the inductance of the loop circuit can be made small.
In accordance with a semiconductor device according to the second aspect of the present invention, the resin package is in a box shape and the main surface of the other end of each of the plurality of main electrode plates alone is exposed on the upper surface of the resin package and, therefore, the package has a simple shape of which the structure is physically strong.
In accordance with a semiconductor device according to the third aspect of the present invention, the exposure position of the main surface of the other end of each of the plurality of main electrode plates is a position at a distance away from an edge on the upper surface of the resign package and, therefore, in the case that the resin package is attached to a heat sink, the distance for isolation from the heat sink to the main electrode plates can be easily secured so that a semiconductor device which can withstand a high voltage, even though the thickness of the resin package thereof is small, can be gained.
In accordance with a semiconductor device according to the fourth aspect of the present invention, the resin package has a body part in a box shape and a plurality of protruding electrode parts which, respectively, protrude from the upper surface of the body part and, therefore, in the case that the resin package is attached to a heat sink, the distance for isolation from the heat sink to the main electrode plates can be more easily secured so that a semiconductor device which can withstand a high voltage, even though the thickness of the body part thereof is small, can be gained. Then because of the existence of the protruding electrode parts, the thickness of the body part, wherein the radiation substrate is buried, can be set at the minimum and, therefore, even in the case that a temperature change occurs due to the heat emission at the time when the device is employed, a warp can be prevented from occurring over the entire resin package and the radiation from the semiconductor device to the heat sink can be prevented from lowering in the efficiency so that the temperature of the semiconductor device can be prevented from increasing to the allowable limit or higher.
In accordance with a semiconductor device according to the fifth aspect of the present invention, the plurality of protruding electrode parts are formed so that the bordering parts vis-à-vis the body part have curved surfaces and, therefore, in the case that, for example, a main electrode plate and an exterior conductor are fastened with a bolt in a protruding electrode part, even though the bolt is squeezed with a large torque, the stress caused in the border part between the body part and the protruding electrode part becomes small so that the protruding electrode part can withstand the squeeze pressure of the bolt, even though the dimension of the protruding electrode part is small, so as to be able to achieve the miniaturization of the semiconductor device.
In accordance with a semiconductor device according to the sixth aspect of the present invention, the plurality of protruding electrode parts have cavities inside thereof and, therefore, it becomes possible to provide nuts in the cavities so that a main electrode plate and an exterior conductor are tightened with a bolt and, thereby, the exterior conductor and the main electrode plate can be connected through a small contact resistance.
In accordance with a semiconductor device according to the seventh aspect of the present invention, the other end of each of the plurality of main electrode plates has a through hole and the through hole has a thread around the inner surface thereof and, therefore, at the time when a main electrode plate and an exterior conductor are fastened with a bolt, it is not necessary to prepare a nut, increasing the ease of assembly.
In accordance with a semiconductor device according to the eighth aspect of the present invention, the through hole is created by means of a burring process and the thread is provided on a burring part and, therefore, a thread can be formed even when the thickness of the main electrode plate is small.
In accordance with a semiconductor device according to the ninth aspect of the present invention, the plurality of protruding electrode parts have nuts buried therein so that the thread of each of the nuts are connected to that of the through hole and, therefore, at the time when a main electrode plate and an exterior conductor are fastened with a bolt, it is not necessary to prepare a nut, increasing the ease of assembly.
In accordance with a semiconductor device according to the tenth aspect of the present invention, the semiconductor device comprises a control circuit which is provided on the radiation substrate and which carries out a driving control of the semiconductor elements and, therefore, the control circuit is provided in the vicinity of the semiconductor elements so that the area of a control wire loop formed between the control circuit and the semiconductor elements can be made small in comparison with the case where the control circuit is provided outside of the semiconductor device and even in the case that a large amount of electromagnetic noise occurs, for example, in a switching element for a heavy current, a voltage fluctuation can be prevented from occurring in the control signal.
In accordance with a semiconductor device according to the eleventh aspect of the present invention, the control circuit is covered with a resin of which the viscosity is smaller than that of the mold resin of the resin package and, therefore, even a control circuit under the condition of a semiconductor chip which is not packaged can be protected from the pressure of the mold resin at the time of the formation of the resin package.
In accordance with a semiconductor device according to the twelfth aspect of the present invention, the bottom surface of the radiation substrate is exposed from the bottom surface of the resin package and an insulating layer is provided so as to, at least, completely cover the bottom surface of the radiation substrate and, therefore, no void occurs within the mold resin, which may possibly occur in a structure where the radiation substrate is buried in the resin package, thus enhancing productivity.
In accordance with a semiconductor device according to the thirteenth aspect of the present invention, the insulating layer is formed of an insulating material in a sheet form that is attached to the bottom surface of the resin package and, therefore, the formation is simple and the thickness thereof can be made even.
In accordance with a semiconductor device according to the fourteenth aspect of the present invention, the bottom surface of the resin package has a step region which is recessed and corresponds to the exposure region of the bottom surface of the radiation substrate and the depth of the step region is lower than the thickness of the insulating layer and, therefore, for example, at the time when the semiconductor device is attached to a heat sink, they are fastened with a bolt, or the like, until the resin package around the step region completely touches the heat sink and, thereby, the insulating layer is compressed so that the thickness thereof becomes equal to the depth of the step region. Accordingly, the depth of the step region is set at a value equal to the minimum thickness of the insulating layer for securing the insulation and the bolt is fastened until the resin package completely touches the heat sink and, thereby, the insulating layer can be prevented from becoming thinner than the minimum thickness due to unevenness of fastening and, in addition, it becomes unnecessary to include an additional margin to the thickness of the insulating layer and, thus, the radiation can be increased.
In accordance with a semiconductor device according to the fifteenth aspect of the present invention, the bottom surface of the resin package has a plurality of protruding parts which are provided so as to surround the exposure region of the bottom surface of the radiation substrate and the height of the protruding parts is lower than the thickness of the insulating layer and, therefore, for example, at the time when the semiconductor device is attached to a heat sink, they are fastened with a bolt, or the like, until the protruding parts completely touches the heat sink and, thereby, the insulating layer is compressed so that the thickness thereof can be made equal to the height of the protruding parts, and as a result, the insulating layer can be prevented from becoming thinner than the minimum thickness due to the unevenness of the fastening and, in addition, it becomes unnecessary to include a margin of the thickness of the insulating layer more than necessary so as to be able to increase the radiation.
In accordance with a semiconductor device according to the sixteenth aspect of the present invention, the semiconductor device further comprises a radiation plate which closely contacts on the insulating layer and of which the area is broader than that of the insulating layer and, therefore, for example, at the time when the semiconductor device is attached to a heat sink, the contact area with the heat sink increases and the radiation can be increased.
In accordance with a semiconductor device according to the seventeenth aspect of the present invention, by making small the intervals between the plurality of radiation substrates, the area of the device can be made small in comparison with the case where a plurality of independent semiconductor devices are combined so that miniaturization, weight reduction and cost reduction can be achieved.
In accordance with a semiconductor device according to the eighteenth aspect of the invention, the area of a circuit loop formed of a main current path of a semiconductor element starting from a main electrode plate and reaching to a different main electrode plate via the semiconductor element and a radiation substrate as well as a main current path with respect to the semiconductor element provided on the adjacent radiation substrate can be made small so that the inductance of the loop circuit can be made small. As a result, the power loss in the semiconductor elements is reduced so that the amount of heat emitted in the semiconductor device can be made small.
The present invention is provided in order to solve the above described problems and the purpose of the invention is to provide a semiconductor device which satisfies both requirements for radiation and for miniaturization while having a semiconductor element for a heavy current.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.